As known, in a mobile communication network, in particular a LTE (Long Term Evolution) mobile communication network, proximity services (ProSE) are services that may be provided by the network operator on the basis of at least two user equipment (UE) being in proximity to each other. The communication network typically comprises a logical function, the ProSe function, which controls the capability of a UE to discover other UEs that are in its proximity and, on the basis of this information, provide and/or receive pre-determined services. These services may be related to business and commercial activities (shops, restaurants, etc.) and the discovery procedure may be used to trigger mobile advertising.
In particular, the direct discovery standardized by 3GPP (3rd Generation Partnership Project) in the technical specification ETSI TS 123 303 v13.4.0 (2016 July), section 5.3, pages 44-99, is the process that allows a UE to detect and identify another UE in proximity using the LTE radio interface, i.e. using E-UTRA (Evolved UMTS Terrestrial Radio Access) radio signals. The direct discovery may comprise two procedures:                announcing, according to which a UE of a subscriber wanting to provide certain information to UEs in proximity receives from the network (i.e. from the ProSe function) over an LTE traffic channel a bit sequence (ProSe application code) that will be broadcasted by the UE using a E-UTRA radio signal;        monitoring/reporting, according to which a UE receives from the ProSe Function over an LTE traffic channel a bit sequence (ProSe discovery filter) that allows monitoring pre-determined ProSe application codes transmitted by UEs that are in its proximity. When the UE receives a ProSe application code that matches the discovery filter, the UE reports the matching ProSe application code to the network and the network provides the UE with information (e.g. advertisements) associated with the UE that is transmitting the matching ProSe application code.Moreover, it is also known that the Wi-Fi Neighbor Awareness Networking (NAN) technology provides a device-to-device (D2D) discovery mechanism, based on the Wi-Fi® technology, for enabling UEs to access proximity services. For instance, these services may be related to social networking, mobile advertising, gaming, dating, etc. This technology allows the so-called “over-the-top” service providers (e.g. Google, Facebook) to use application servers to deliver proximity services to their users across an IP network (e.g. Internet).        